Coagulants are used to clarify industrial waste water having high turbidity. Organic coagulants have received considerable attention as replacement of inorganic coagulants (e.g., aluminum sulfate, polyaluminum chloride and ferric chloride). Although inorganic coagulants are less expensive, they are less efficient and result in a larger volume of sludge which needs further treatment. U.S. Pat. No. 4,155,847 discloses cationic coagulants which are water-soluble polymers made from polycondensation of epihalohydrin and amines. U.S. Pat. Nos. 3,784,493, 3,912,706, 4,017,419, 4,017,475, 4,455,257, 4,739,040 and 4,775,744 describe the Mannich reaction products of lignin-based materials with amines (including monoamines and polyamines) and can be characterized as in Reaction I:
where R1 and R2 may be the same or different and selected from the group consisting of hydrogen, methyls, ethyls, alkyls, hydroxyl-substituted alkyls, and alkoxy-substituted alkyls of 1 to 20 carbon atoms; the alkyl groups may be straight or branched alkyl groups; or a cycloalkyl ring. The lignin may be repeating units of a Kraft lignin or lignosulfonate from softwood or hardwood. The functional groups in the these lignins include, but are not limited to, hydrogen, alkyl groups that are straight or branched, or cycloalkyl rings, for example, phenolic, hydroxyl, methoxyl, carboxyl, catechol, and sulfonate groups. A more thorough technical description of lignins can be found in Lebo, S. E., Gargulak, J. D. and McNally, T. J. 2001. Lignin. Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley & Sons.
The resulting cationic lignin-amines are useful as coagulants as well as setting control agents, surfactants, fillers for resins. Formaldehyde, however, was recently identified as a carcinogen. Thus, there is a need for cationic lignin-amine production processes that do not use formaldehyde.